Mr. Delligatti celebrated his birthday in 2008 with a cake that looked like a Big Mac.

WASHINGTON — Neither the humpbacked 747 nor the cherry-red public buses that crisscross London surpass the Big Mac as the world’s most famous double-decker. Ever since Jim Delligatti, who died Monday at 98, created the sandwich in 1967 at a McDonald’s franchise near Pittsburgh, it has been the flagship item of the global fast-food chain, selling more than a half-billion servings annually in the United States alone.

The Big Mac has been called the ‘‘Elvis of sandwiches,’’ the ‘‘Paul Bunyan of hamburgers.’’ It’s the solid-food equivalent of Coca-Cola, a totem of consistency instantly recognizable from western Pennsylvania to India, where cows are considered sacred by the nation’s Hindu population and where the Big Mac is made with mutton or chicken and called the Maharaja Mac. President Clinton, the onetime burger devourer in chief, was known to indulge his ‘‘Big Mac Attack,’’ as one memorable advertising campaign described such cravings.

Mr. Delligatti’s creation, a sensation from the start, was the subject of a legendary advertising campaign in 1974. The inescapable jingle mirrored the essential excess of the Big Mac itself, making one word of its ingredients — ‘‘twoallbeefpattiesspecialsauce- lettucecheesepicklesonionsona-sesameseedbun’’ — and daring people to pronounce it. (A follow-up spot featured people struggling to master the tongue-twister.)

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The sesame seeds atop the bun were the pièce de résistance, a simple but decadent touch that marked the sandwich’s status as the grandee on the McDonald’s menu. For the company, the Big Mac was a shot across the bow to Burger King’s Whopper, created a decade earlier.

The Big Mac became a baby boomer favorite, then a Generation X delight, then a Millennial treat, and on it went, even as grass-fed, antibiotic-free meat ate into Big Mac’s primacy and McDonald’s sustained withering attacks from critics. The film ‘‘Super Size Me’’ (2004), in which documentarian Morgan Spurlock risks his health to subsist on McDonald’s for a month, and Eric Schlosser’s book ‘‘Fast Food Nation’’ (2001) found deep fault with many of the company’s products.

Marion Nestle, a New York University nutrition and public health professor, wrote in an e-mail: ‘‘The Big Mac has had an enormous influence on American — and international — eating patterns, not all to the good alas. It’s become a synonym — the prototype, an American icon — for junk food.’’

From any perspective, Mr. Delligatti’s legacy amounted to much more than a meal. The Economist magazine began printing its annual ‘‘Big Mac Index’’ three decades ago, tracking the cost of the burger across the globe.

Mr. Delligatti conceived the burger in a simple effort to grow business at his franchises in the western Pennsylvania.

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The sandwich (29 cents with coupon) sold so well — with profits reportedly jumping by 12 percent — that Mr. Delligatti began to feature it at his other franchises. The company introduced it nationally in 1968, for 49 cents, and sold it under various names.

Mr. Delligatti acknowledged a debt to Bob Wian, who operated a Glendale, Calif., hamburger stand and crafted a similar double-decker burger in the late 1930s that became the signature item of Bob’s Big Boy restaurants.

‘‘This wasn’t like discovering the lightbulb,’’ Mr. Delligatti later told the Los Angeles Times. ‘‘The bulb was already there. All I did was screw it in the socket.’’